I'm trying to get my head around this..
My Smartcharger charges agm at a higher voltage than lead acid
My understanding is that it is ok to use agm with a vsr unit (lead acid starter) on the proviso that it is removed occasionally and charged properly i believe this is because the alternator doesn't give enough voltage to charge the Agm properly 14.6v required for the agm according to Ring.
Is this correct?
Twin batteries
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Timandclaire
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g8dhe
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Re: Twin batteries
No.
The AGM batteries need to have the voltage dropped down from 14.4 volts once they are fully charged to around the float charge level 13.5-13.6 volts.
The reason is that there is a lot less electrolyte in an AGM cell as its held in place by the glass mat material between the plates, this means that any gassing that occurs (Gassing starts from 14.4 volts and becomes excessive by 14.6 volts) significantly reduces the electrolyte level, which being sealed can't be replaced!
See these pages for the full info. https://batteryuniversity.com/learn/art ... ss_mat_agm
This is also a handy sheet to bookmark https://www.victronenergy.com/upload/do ... ies-EN.pdf
The AGM batteries need to have the voltage dropped down from 14.4 volts once they are fully charged to around the float charge level 13.5-13.6 volts.
The reason is that there is a lot less electrolyte in an AGM cell as its held in place by the glass mat material between the plates, this means that any gassing that occurs (Gassing starts from 14.4 volts and becomes excessive by 14.6 volts) significantly reduces the electrolyte level, which being sealed can't be replaced!
See these pages for the full info. https://batteryuniversity.com/learn/art ... ss_mat_agm
This is also a handy sheet to bookmark https://www.victronenergy.com/upload/do ... ies-EN.pdf
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Timandclaire
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- Posts: 29
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Re: Twin batteries
Right that makes sense so the solution would be a lead acid + vsr for running lights/12v sockets etc and a separate agm for fridge/coolbox which would be charged at home on a smartcharger or via solar with some sort of voltage regulation
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g8dhe
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Re: Twin batteries
Yes that would be away of doing it, even if it makes the system a lot more complicated, BUT do remember that these "intelligent" chargers are anything but intelligent, they use charging time as measured by the charger to calculate how long they need to push the maximum charging current thru the battery this means that if you are drawing power from the system at the same time as your charging the charger will get it TOTALLY WRONG! The same if you have multiple charging sources like a Mains charger and a Solar panel charger, its quite possible that the two chargers will try to push TWICE the current thru the battery if working together and totally kill the battery in doing so 
You need to bear in mind that the manufacturers expect you to Charge-Store-Use-Charge-Store-Use the batteries they don't plan on you Charging and Using at the same time or that you would even contemplate having multiple charging sources operating at the same time, plus of course they are trying to SELL you there batteries, whilst trying to convince you that they will last a lot longer, have more charge cycles etc etc.
Lead Acid batteries are a very mature technology, all the possible improvements have been well tested and generally only bring about a small improvement in performance - despite what the salesman would have you believe - in general the improvements are at the cost of other parameters (like sealed for life - Oh I can't refill then!), look carefully at Capacity measurements who would think of quoting the 100% battery capacity at 50°C (dropping to 80% at 25°C) ? Please tell me which country even reaches that temperature in normal working!!!!
You need to do your own research, I have spent some time doing this and now use cheap, simple, flooded sealed batteries and plan to replace every 2 years but sometimes find they last 3 years the batteries I buy cost around £90 mark sometimes even less. I don't need intelligent chargers, I use three sources of power at the same time and they still last ......
You need to bear in mind that the manufacturers expect you to Charge-Store-Use-Charge-Store-Use the batteries they don't plan on you Charging and Using at the same time or that you would even contemplate having multiple charging sources operating at the same time, plus of course they are trying to SELL you there batteries, whilst trying to convince you that they will last a lot longer, have more charge cycles etc etc.
Lead Acid batteries are a very mature technology, all the possible improvements have been well tested and generally only bring about a small improvement in performance - despite what the salesman would have you believe - in general the improvements are at the cost of other parameters (like sealed for life - Oh I can't refill then!), look carefully at Capacity measurements who would think of quoting the 100% battery capacity at 50°C (dropping to 80% at 25°C) ? Please tell me which country even reaches that temperature in normal working!!!!
You need to do your own research, I have spent some time doing this and now use cheap, simple, flooded sealed batteries and plan to replace every 2 years but sometimes find they last 3 years the batteries I buy cost around £90 mark sometimes even less. I don't need intelligent chargers, I use three sources of power at the same time and they still last ......